Rates of substance use disorders (SUDS) are high among military personnel and veterans. While much research is focused on the acute care of SUDs, the risk of relapse to substance use following treatment is high and attention to continuing care is critical. New continuing care strategies targeting life-style change and improved coping mechanisms are important in facilitating maintenance of abstinence, promoting rehabilitation and functional recovery for veterans with SUDs. Mindfulness-based relapse prevention (MBRP), a manualized treatment integrating cognitive-behavioral relapse prevention therapy with mindfulness practices, has shown promise in continuing care for SUDs. The proposed project will compare MBRP to a 12-Step Facilitation treatment as a continuing care strategy following primary treatment for SUDs. Participants will be randomized to participate in 8-weeks of weekly 90-minute, group-based MBRP or 12-Step Facilitation followed by a 10- month follow-up period with regular assessments of substance use, mood/anxiety symptoms, quality of life and functional outcomes. Two VAMC sites (Charleston and Tuscaloosa) with a history of successful collaboration will work together to recruit an adequate sample size to address the primary study questions within a 4-year period and to ensure generalizability of the results. If this trial demonstrates that MBRP promotes sustained abstinence and improved functional outcomes, this will provide a valuable treatment to facilitate rehabilitation and recovery for veterans with SUDs.